There is an ongoing concern in the tobacco industry to produce cigarettes having wrappers which reduce the ignition proclivity of the smoking article, or the tendency of the smoking article to ignite surfaces which come into contact with the lit smoking article. Reports have been made of fires attributed to burning cigarettes coming into contact with combustible materials. A justifiable interest exists in the industry to reduce the tendency of cigarettes, or other smoking articles to ignite surfaces and materials used in furniture, bedding, and the like upon contact.
Thus, a desirable feature of smoking articles, particularly cigarettes, is that they tend to self-extinguish upon being dropped or left in a free burning state on combustible materials.
It has long been recognized in the tobacco industry that the cigarette wrapper can have a significant influence on the smolder characteristics of the cigarette. In this regard, various attempts have been made in the art to alter or modify the cigarette wrappers in order to achieve the desired tendency of the cigarette to self-extinguish, or in other words to reduce the ignition proclivity characteristics of cigarettes.
The prior art describes the application of film-forming compositions or alternatively cellulosic fibrous compositions to cigarette paper to reduce the paper permeability and control the burn rate. It has been shown that when these materials have been applied in discrete areas along the length of the cigarette, the cigarette shows a reduced propensity to ignite a substrate and tends to self-extinguish.
U.S. Pat. No. 5,878,753 to Peterson et al., U.S. Pat. No. 6,779,530 to Kraker, and U.S. Pat. No. 6,725,867 to Peterson et al., which are incorporated herein by reference, for example, describe a smoking article wrapper being treated with a film-forming composition to reduce ignition proclivity. U.S. Pat. No. 5,878,754 to Peterson et al. which is also incorporated herein by reference describes a smoking article wrapper being treated with a non-aqueous solution of a solvent soluble polymer dissolved in a non-aqueous solution to reduce ignition proclivity.
Although the above patents have provided great advancements in the art, further improvements are still needed. For instance, the discrete areas formed on the wrapper that are intended to reduce ignition proclivity can have various adverse effects on the smoking article. The treated discrete areas, for instance, generally have a lower permeability than the base wrapper. The lower permeability in the treated areas can have an adverse impact upon the enjoyment of the smoking article, creating mainstream smoke with a harsh taste in comparison to the remainder of the smoking article.
In the past, in order to counteract some of the above effects, treated discrete areas were produced having a permeability that gradually changed from a minimum to a maximum over the width of the treated discrete areas in the direction of the burning coal. This arrangement has provided various improvements.
In the past, particular film-forming compositions have been proposed that contain a film-forming material having a relatively low molecular weight. These film-forming compositions were applied to the wrapper at relatively high solids concentrations. This arrangement also allowed for some improvement in controlling permeability of the treated discrete areas.
Further improvements, however, are still needed. For instance, a need exists for a wrapper for a smoking article having treated discrete areas in which the treated discrete areas have a relatively high permeability. Specifically, a need exists for a method of increasing the permeability in the treated areas without having to be limited to particular film-forming materials.
A need also exists for producing treated discrete areas on a wrapper that reduce the ignition proclivity of a smoking article to desired levels while having a minimal impact upon permeability and while also using a minimal amount of material added to the wrapper.